Method of treating subterranean formations with porous ceramic particulate materials

ABSTRACT

Methods and compositions useful for subterranean formation treatments, such as hydraulic fracturing treatments and sand control that include porous materials. Such porous materials may be selectively configured porous material particles manufactured and/or treated with selected glazing materials, coating materials and/or penetrating materials to have desired strength and/or apparent density to fit particular downhole conditions for well treating such as hydraulic fracturing treatments and sand control treatments. Porous materials may also be employed in selected combinations to optimize fracture or sand control performance, and/or may be employed as relatively lightweight materials in liquid carbon dioxide-based well treatment systems.

[0001] This application claims priority to provisional applicationserial No. 60/407,734, filed on Sep. 3, 2002 and provisional applicationserial No. 60/428,836, filed on Nov. 25, 2002.

FIELD OF THE INVENTION

[0002] This invention relates generally to methods and compositionsuseful for subterranean formation treatments, such as hydraulicfracturing treatments and sand control.

BACKGROUND OF THE INVENTION

[0003] Hydraulic fracturing is a common stimulation technique used toenhance production of fluids from subterranean formations. In a typicalhydraulic fracturing treatment, fracturing treatment fluid containing asolid proppant material is injected into the formation at a pressuresufficiently high enough to cause the formation or enlargement offractures in the reservoir. During a typical fracturing treatment,proppant material is deposited in a fracture, where it remains after thetreatment is completed. After deposition, the proppant material servesto hold the fracture open, thereby enhancing the ability of fluids tomigrate from the formation to the well bore through the fracture.Because fractured well productivity depends on the ability of a fractureto conduct fluids from a formation to a wellbore, fracture conductivityis an important parameter in determining the degree of success of ahydraulic fracturing treatment.

[0004] Hydraulic fracturing treatments commonly employ proppantmaterials that are placed downhole with a gelled carrier fluid such asaqueous-based fluid such as gelled brine. Gelling agents for proppantcarrier fluids may provide a source of proppant pack and/or formationdamage, and settling of proppant may interfere with proper placementdownhole. Formation damage may also be caused by gelled carrier fluidsused to place particulates downhole for purposes such as for sandcontrol, such as gravel packs, frac packs, and similar materials.Formulation of gelled carrier fluids usually requires equipment andmixing steps designed for this purpose.

[0005] Hydraulic fracturing treatments may also employ proppantmaterials that are placed downhole with non-aqueous-based fluids, suchas liquid CO₂ and liquid CO₂/N₂ systems. Proppants commonly employedwith such non-aqueous-based fluids tend to settle in the system.

[0006] Many different materials have been used as proppants includingsand, glass beads, walnut hulls, and metal shot. Commonly used proppantstoday include various sands, resin-coated sands, intermediate strengthceramics, and sintered bauxite; each employed for their ability to costeffectively withstand the respective reservoir closure stressenvironment. As the relative strength of the various materialsincreases, so too have the respective particle densities, ranging from2.65 g/cc for sands to 3.4 g/cc for the sintered bauxite. Unfortunately,increasing particle density leads directly to increasing degree ofdifficulty with proppant transport and a reduced propped fracture volumefor equal amounts of the respective proppant, reducing fractureconductivity. Previous efforts undertaken to employ lower densitymaterials as proppant have generally resulted in failure due toinsufficient strength to maintain fracture conductivity at even thelowest of closure stresses (1,000 psi).

[0007] Recently, deformable particles have been developed. Suchdeformable particles for sand flowback control are significantly lighterthan conventional proppants, and exhibit high compressive strength Suchdeformable materials include polystyrene divinylbenzene (PSDVB)deformable beads. Such beads, however, have not been entirely successfulprimarily due to limitations of the base material. While PSDVB beadsoffered excellent deformability and elasticity, they lacked thestructural integrity to withstand high closure stresses andtemperatures.

[0008] The first successful path to generate functional deformableparticles was the usage of modified ground walnut hulls. Walnut hulls intheir natural state have been used as proppants, fluid loss agents andlost circulation materials for many years with greater or lesser degreesof success in each respective task. As a proppant, natural walnut hullshave very limited applicability, because they deform fairly readily uponapplication of closure stress. This deformation drastically reducesconductivity and limits utility of the natural material to relativelylow-closure environments.

[0009] Walnut hull based ultra-lightweight (UCW) proppants may bemanufactured in a two-step process by using closely sized walnutparticles (i.e. 20/30 US mesh), and impregnating them with strong epoxyor other resins. These impregnated walnut hull particles are then coatedwith phenolic or other resins in a fashion similar to most resin coatedproppants (RCP). Such walnut hull based ULW proppants have a bulkdensity of 0.85 grams/cc and withstand up to 6,000 psi (41.4 MPa)closure stress at 175° F. (79° C.).

[0010] Generally speaking, the stronger a proppant, the greater thedensity. As density increases, so too does the difficulty of placingthat particle evenly throughout the created fracture geometry. Excessivesettling can often lead to bridging of the proppant in the formationbefore the desired stimulation is achieved. The lower particle densityreduces the fluid velocity required to maintain proppant transportwithin the fracture, which, in turn, provides for a greater amount ofthe created fracture area to be propped.

[0011] ULW proppants which allow for optimization of fracturingtreatment with improved fracture length and well productivity aretherefore desired.

SUMMARY OF THE INVENTION

[0012] The invention relates to methods for treating subterraneanformations by treating a well with a composition containing porousceramic or organic polymeric particulates. In particular, thecompositions introduced into the well are particularly suitable inhydraulic fracturing of a well as well as sand consolidation methodssuch as gravel packing and frac packing. The porous particulate materialmay be a selectively configured porous particulate material, as definedherein. Alternatively, the porous particulate material may be anon-selectively configured porous particulate material, as definedherein.

[0013] The porous particulate material may be selectively configuredwith a non-porous penetrating material, coating layer or glazing layer.In a preferred embodiment, the porous particulate material is aselectively configured porous particulate material wherein either (a.)the apparent density or apparent specific gravity of the selectivelyconfigured porous particulate material is less than the apparent densityor apparent specific gravity of the porous particulate material; (b.)the permeability of the selectively configured porous particulatematerial is less than the permeability of the porous particulatematerial; or (c.) the porosity of the selectively configured porousparticulate material is less than the porosity of the porous particulatematerial.

[0014] In a preferred embodiment, the penetrating material and/orcoating layer and/or glazing layer of the selectively configured porousparticulate material is capable of trapping or encapsulating a fluidhaving an apparent specific gravity less than the apparent specificgravity of the carrier fluid. Further, the coating layer and/orpenetrating material and/or glazing material may be a liquid having anapparent specific gravity less than the apparent specific gravity of thematrix of the porous particulate material.

[0015] The strength of the selectively configured porous particulatematerial is typically greater than the strength of the porousparticulate material per se. Further, the selectively configured porousmaterial exhibits crush resistance under conditions as high as 10,000psi closure stress, API RP 56 or API RP 60.

[0016] In a preferred mode, the porous particulate composition is asuspension of porous particulates in a carrier fluid. The suspensionpreferably forms a pack of particulate material that is permeable tofluids produced from the wellbore and substantially prevents or reducesproduction of formation materials from the formation into the wellbore.

[0017] Further, the porous particulate material may exhibit a porosityand permeability such that a fluid may be drawn at least partially intothe porous matrix by capillary action. Preferably, the porousparticulate material has a porosity and permeability such that apenetrating material may be drawn at least partially into the porousmatrix of the porous particulate material using a vacuum and/or may beforced at least partially into the porous matrix under pressure.

[0018] The selectively configured porous particulate material mayconsist of a multitude of coated particulates bonded together. In suchmanner, the porous material is a cluster of particulates coated with acoating or penetrating layer or glazing layer. Suitable coating layersor penetrating materials include liquid and/or curable resins, plastics,cements, sealants, or binders such as a phenol, phenol formaldehyde,melamine formaldehyde, urethane, epoxy resin, nylon, polyethylene,polystyrene or a combination thereof. In a preferred mode, the coatinglayer or penetrating material is an ethyl carbamate-based resin.

[0019] In a preferred embodiment, the selectively configured porousparticulate materials are derived from lightweight and/or substantiallyneutrally buoyant particles. The application of selected porous materialparticulates and relatively lightweight and/or substantially neutrallybuoyant particulate material as a fracture proppant particulateadvantageously provides for substantially improved overall systemperformance in hydraulic fracturing applications, or in other welltreating applications such as sand control.

[0020] The porous particulate material-containing compositions used inthe invention may further contain a carrier fluid. The carrier fluid maybe a completion or workover brine, salt water, fresh water, a liquidhydrocarbon, or a gas such as nitrogen or carbon dioxide.

[0021] The porous particulate material-containing compositions mayfurther contain a gelling agent, crosslinking agent, gel breaker,surfactant, foaming agent, demulsifier, buffer, clay stabilizer, acid ora mixture thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more fully understand the drawings referred to in thedetailed description of the present invention, a brief description ofeach drawing is presented, in which:

[0023]FIG. 1 is a graph depicting bulk apparent density comparison ofthe data of Example 1.

[0024]FIG. 2 is a graph depicting permeability versus closure stressdata of Example 2.

[0025]FIG. 3 is a graph depicting conductivity versus closure stressdata of Example 2.

[0026]FIG. 4 is a graph depicting conductivity versus closure stressdata of Example 2.

[0027]FIG. 5 is a graph depicting permeability versus closure stressdata of Example 2.

[0028]FIG. 6 is a graph depicting conductivity comparison data ofExample 2.

[0029]FIG. 7 is a graph depicting permeability comparison data ofExample 2.

[0030]FIG. 8 is a SEM photograph of a porous material particle ofExample 3.

[0031]FIG. 9 is a SEM photograph of a porous material particle ofExample 3.

[0032]FIG. 10 is a SEM photograph of a porous material particle ofExample 3.

[0033]FIG. 11 is a SEM photograph of a porous material particle ofExample 3.

[0034]FIG. 12 is a SEM photograph of a porous material particle ofExample 3.

[0035]FIG. 13 is a SEM photograph of a porous material particle ofExample 3.

[0036]FIG. 14 is a SEM photograph of a porous material particle ofExample 3.

[0037]FIG. 15 is a SEM photograph of a porous material particle ofExample 3.

[0038]FIG. 16 illustrates proppant distribution for a selectedcombination of well treatment particulates according to one embodimentof the disclosed compositions and methods described in Example 4.

[0039]FIG. 17 illustrates comparative proppant distribution data ofExample 4 for Ottawa sand alone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] As used herein, the following terms shall have the designatedmeanings:

[0041] “porous particulate material” shall refer to porous ceramic orporous organic polymeric materials. Examples of types of materialssuitable for use as porous material particulates include particulateshaving a porous matrix;

[0042] “selectively configured porous particulate material” shall referto any porous particulate material, natural or non-natural, which hasbeen chemically treated, such as treatment with a coating material;treatment with a penetrating material; or modified by glazing. The termshall include, but not be limited to, those porous particulate materialswhich have been altered to achieve desired physical properties, such asparticle characteristics, desired strength and/or apparent density inorder to fit particular downhole conditions for well treating such ashydraulic fracturing treatments and sand control treatments.

[0043] “non-selectively configured porous particulate material” shallrefer to any porous natural ceramic material, such as lightweightvolcanic rocks, like pumice, as well as perlite and other porous “lavas”like porous (vesicular) Hawaiian Basalt, porous Virginia Diabase, andUtah Rhyolite. Further, inorganic ceramic materials, such as alumina,magnetic glass, titanium oxide, zirconium oxide, and silicon carbide mayalso be used. In addition, the term shall refer to a synthetic porousparticulate material which has not been chemically treated and whichimparts desired physical properties, such as particle characteristics,desired strength and/or apparent density in order to fit particulardownhole conditions for well treating;

[0044] “relatively lightweight” shall refer to a porous particulatematerial that has a apparent density (API RP 60) that is substantiallyless than a conventional particulate material employed in hydraulicfracturing or sand control operations, such as sand having an apparentspecific gravity (API RP 60) of 2.65 and bauxite having an apparentspecific gravity of 3.55. The apparent specific gravity of a relativelylightweight material is less than about 2.4.

[0045] “substantially neutrally buoyant” shall refer to a porousparticulate material that has an apparent density sufficiently close tothe apparent density of a selected ungelled or weakly gelled carrierfluid, such as an ungelled or weakly gelled completion brine, otheraqueous-based fluid, slick water, or other suitable fluid, which allowspumping and satisfactory placement of the proppant/particulate using theselected ungelled or weakly gelled carrier fluid.

[0046] a “weakly gelled carrier fluid” is a carrier fluid having aviscosifier or friction reducer to achieve friction reduction whenpumped down hole, for example when pumped down tubing, work string,casing, coiled tubing, drill pipe, or similar location, wherein thepolymer or viscosifier concentration from about 0 pounds of polymer perthousand gallons of base fluid to about 10 pounds of polymer perthousand gallons of base fluid, and/or the viscosity from about 1 toabout 10 centipoises. An “ungelled carrier fluid” is a carrier fluidhaving no polymer or viscosifier. The ungelled carrier fluid may containa friction reducer known in the art.

[0047] The selectively configured porous particulate materials as wellas non-selectively configured porous particulate materials areparticularly effective in hydraulic fracturing as well as sand controlfluids such as water, salt brine, slickwater such as slick waterfracture treatments at relatively low concentrations to achieve partialmonolayer fractures, low concentration polymer gel fluids (linear orcrosslinked), foams (with gas) fluid, liquid gas such as liquid carbondioxide fracture treatments for deeper proppant penetration, treatmentsfor water sensitive zones, and treatments for gas storage wells.

[0048] For instance, the selectively configured porous materialparticles or non-selectively configured porous material particles may bemixed and pumped during any desired portion/s of a well treatment suchas hydraulic fracturing treatment or sand control treatment and may bemixed in any desired concentration with a carrier fluid. In this regard,any carrier fluid suitable for transporting the selectively configuredporous particulate material or non-selectively configured porousparticulate material particles into a well and/or subterranean formationfracture in communication therewith may be employed including, but notlimited to, carrier fluids comprising salt water, fresh water, potassiumchloride solution, a saturated sodium chloride solution, liquidhydrocarbons, and/or nitrogen or other gases may be employed. Suitablecarrier fluids include or may be used in combination with fluids havegelling agents, cross-linking agents, gel breakers, surfactants, foamingagents, demulsifiers, buffers, clay stabilizers, acids, or mixturesthereof.

[0049] When used in hydraulic fracturing, the selectively configuredporous particulate material or non-selectively configured porousparticulate material particles may be injected into a subterraneanformation in conjunction with a hydraulic fracturing treatment or othertreatment at pressures sufficiently high enough to cause the formationor enlargement of fractures. Such other treatments may be near wellborein nature (affecting near wellbore regions) and may be directed towardimproving wellbore productivity and/or controlling the production offracture proppant or formation sand. Particular examples include gravelpacking and “frac-packs.” Moreover, such particles may be employed aloneas a fracture proppant/sand control particulate, or in mixtures inamounts and with types of fracture proppant/sand control materials, suchas conventional fracture or sand control particulate. Furtherinformation on hydraulic fracturing methods and materials for usetherein may be found in U.S. Pat. No. 6,059,034 and in U.S. Pat. No.6,330,916, which are incorporated herein by reference.

[0050] When employed in well treatments, selected porous materialparticles that have been selectively configured, such as glazed and/ortreated with one or more selected coating and/or penetrating materials,may be introduced into a wellbore at any concentration/s deemed suitableor effective for the downhole conditions to be encountered. For example,a well treatment fluid may include a suspension of proppant or sandcontrol particulate that is made up completely of relatively lightweightselected porous material particles that have been selectivelyconfigured, such as glazed and/or treated with one or more selectedcoating and/or penetrating materials. Alternatively, it is possible thata well treatment fluid may include a suspension that contains a mixtureof conventional fracture proppant or sand control particulates such assand with relatively lightweight selected porous material particles thathave been selectively configured such as glazed and/or treated with oneor more selected coating and/or penetrating materials.

[0051] In one exemplary embodiment, a gravel pack operation may becarried out on a wellbore that penetrates a subterranean formation toprevent or substantially reduce the production of formation particlesinto the wellbore from the formation during production of formationfluids. The subterranean formation may be completed so as to be incommunication with the interior of the wellbore by any suitable methodknown in the art, for example by perforations in a cased wellbore,and/or by an open hole section. A screen assembly such as is known inthe art may be placed or otherwise disposed within the wellbore so thatat least a portion of the screen assembly is disposed adjacent thesubterranean formation. A slurry including the selectively configuredporous particulate material or non-selectively configured porousparticulate material and a carrier fluid may then be introduced into thewellbore and placed adjacent the subterranean formation by circulationor other suitable method so as to form a fluid-permeable pack in anannular area between the exterior of the screen and the interior of thewellbore that is capable of reducing or substantially preventing thepassage of formation particles from the subterranean formation into thewellbore during production of fluids from the formation, while at thesame time allowing passage of formation fluids from the subterraneanformation through the screen into the wellbore. It is possible that theslurry may contain all or only a portion of selectively configuredporous particulate material or the non-selectively configured porousparticulate material. In the latter case, the balance of the particulatematerial of the slurry may be another material, such as a conventionalgravel pack particulate.

[0052] As an alternative to use of a screen, the sand control method mayuse the selectively configured porous particulate material ornon-selectively configured porous particulate material in accordancewith any method in which a pack of particulate material is formed withina wellbore that it is permeable to fluids produced from a wellbore, suchas oil, gas, or water, but that substantially prevents or reducesproduction of formation materials, such as formation sand, from theformation into the wellbore. Such methods may or may not employ a gravelpack screen, may be introduced into a wellbore at pressures below, at orabove the fracturing pressure of the formation, such as frac pack,and/or may be employed in conjunction with resins such as sandconsolidation resins if so desired.

[0053] The porous particulate material shall include any naturallyoccurring or manufactured or engineered porous ceramic particulatematerial that has an inherent and/or induced porosity. A commerciallyavailable instrument, ACCUPYC 1330 Automatic Gas Pycnometer(Micromeritics, Norcross, Ga.), that uses Helium as an inert gas and themanufacturer's recommended procedure can be used to determine theinternal porosity of the particulates. The internal porosity isgenerally from about 10 to 75 volume percent. Such particulate materialmay also have an inherent or induced permeability, i.e., individual porespaces within the particle are interconnected so that fluids are capableof at least partially moving through the porous matrix, such aspenetrating the porous matrix of the particle, or may have inherent orinduced non-permeability, individual pore spaces within the particle aredisconnected so that fluids are substantially not capable of movingthrough the porous matrix, such as not being capable of penetrating theporous matrix of the particle. The degree of desired porosityinterconnection may be selected and engineered into the non-selectivelyconfigured porous particulate material. Furthermore such porousparticles may be selected to have a size and shape in accordance withtypical fracturing proppant particle specifications (i.e., having auniform shape and size distribution), although such uniformity of shapeand size is not necessary.

[0054] The apparent specific gravity of the porous particulate materialis generally less than or equal to 2.4, preferably less than or equal to2.0, even more preferably less than or equal to 1.75, most preferablyless than or equal to 1.25.

[0055] In a selectively configured porous particulate material, theparticles may be selected based on porosity and/or permeabilitycharacteristics so that they have desired lightweight characteristics,such as when suspended in a selected carrier fluid for a well treatment.As before, the inherent and/or induced porosity of a porous materialparticle may be selected so as to help provide the desired balancebetween apparent density and strength. Optional materials may beemployed along with a glazing, penetrating and/or coating material tocontrol penetration, such as enhancing or impairing penetration. Forexample, in one embodiment an cationic clay stabilizer, such as CLAYMASTER 5C from BJ Services, may be first applied to the exterior surfaceof a porous ceramic material to inhibit penetration bycoating/penetrating material, such as epoxy or resin described elsewhereherein.

[0056] In a preferred embodiment, the porous particulate material is arelatively lightweight or substantially neutral buoyant particulatematerial. Such materials may be employed in a manner that eliminates theneed for gellation of carrier fluid, thus eliminating a source ofpotential proppant pack and/or formation damage. Furthermore, arelatively lightweight particulate material may be easier to placewithin a targeted zone due to lessened settling constraints, and areduced mass of such relatively lightweight particulate material isgenerally required to fill an equivalent volume than is required withconventional sand control particulates, used, for example, for gravelpacking purposes.

[0057] Relatively lightweight and/or substantially neutrally buoyantfracture proppant/particulate material used in hydraulic fracturing/sandcontrol treatment, such as porous ceramic particles having untreatedbulk apparent density of 1.16 and untreated porosity of about 59.3%, maybe employed.

[0058] In one embodiment, the disclosed porous material particulates maybe employed as relatively lightweight particulate/proppant material thatmay be introduced or pumped into a well as neutrally buoyant particlesin, for example, a saturated sodium chloride solution carrier fluid or acarrier fluid that is any other completion or workover brine known inthe art, thus eliminating the need for damaging polymer or fluid lossmaterial. In one embodiment, such a material may be employed asproppant/sand control particulate material at temperatures up to about700° F., and closure stresses up to about 8000 psi. However, theseranges of temperature and closure stress are exemplary only, it beingunderstood that the disclosed materials may be employed as proppant/sandcontrol materials at temperatures greater than about 700° F. and/or atclosure stresses greater than about 8000 psi. In any event, it will beunderstood with benefit of this disclosure that porous particulatematerial and/or coating/penetrating materials may be selected by thoseof skill in the art to meet and withstand anticipated downholeconditions of a given application.

[0059] In those embodiments where the disclosed porous materialparticulates are employed as relatively lightweight and/or substantiallyneutrally buoyant particulate/proppant materials, they may be employedwith carrier fluids that are gelled, non-gelled, or that have a reducedor lighter gelling requirement as compared to carrier fluids employedwith conventional fracture treatment/sand control methods. In oneembodiment employing one or more of the disclosed substantiallyneutrally buoyant particulate materials and a brine carrier fluid,mixing equipment need only include such equipment that is capable of (a)mixing the brine (dissolving soluble salts), and (b) homogeneouslydispersing in the substantially neutrally buoyant particulate material.In one embodiment, a substantially neutrally buoyantparticulate/proppant material may be advantageously pre-suspended andstored in a storage fluid, such as brine of near or substantially equaldensity, and then pumped or placed downhole as is, or diluted on thefly.

[0060] Examples of non-natural porous particulate materials for use inthe invention include, but are not limited to, porous ceramic particlessuch as those particles available from Carbo Ceramics Inc. as“Econoprop”, and those fired kaolinitic described in U.S. Pat. No.5,188,175 which is incorporated herein by reference. As described inthis reference such particles may include solid spherical pellets orparticles from raw materials (such as kaolin clay) having an aluminacontent of between about 25% and 40% and a silica content of betweenabout 50% and 65%. A starch binder may be employed. Such particles maybe characterized as having a ratio of silicon dioxide to alumina contentof from about 1.39 to about 2.41, and a apparent specific gravity ofbetween about 2.20 and about 2.60 or between about 2.20 and about 2.70.

[0061] It will also be understood that porous ceramic particles may beselectively manufactured from raw materials such as those described inU.S. Pat. No. 5,188,175; U.S. Pat. No. 4,427,068; and U.S. Pat. No.4,522,731, which are each incorporated herein by reference, such as byinclusion of selected process steps in the initial materialmanufacturing process to result in a material that possesses desiredcharacteristics of porosity, permeability, apparent density or apparentspecific gravity, combinations thereof. For example, such raw materialsmay be fired at relatively low temperature of about 1235° F. or about1300° F. (or about 700° C.) to achieve a desired crystalline structureand a more highly porous and lighter structure. In one exemplaryembodiment of such particles, as described elsewhere herein, about 20/40mesh size porous material fired kaolinitic particles from Carbo CeramicsInc. may be selected for use in the disclosed method. These particleshave the following internal characteristics: bulk apparent density about1.16, internal porosity about 59.3%. These particles may be treated witha variety of penetrating/coating materials in an amount of from about0.5 to about 10% by total weight of particle. Such coated particles maybe manufactured and/or supplied, for example, by Fritz Industries ofMesquite, Tex.

[0062] In one exemplary case, size of such a material may be selected torange from about 200 mesh to about 8 mesh.

[0063] In such a case, the particles may be selected based on porosityand/or permeability characteristics so that they have desiredlightweight characteristics, such as when suspended in a selectedcarrier fluid for a well treatment. As before, the inherent and/orinduced porosity of a porous material particle may be selected so as tohelp provide the desired balance between apparent density and strength.Optional materials may be employed along with a glazing, penetratingand/or coating material to control penetration such as enhance or impairpenetration. For example, in one embodiment an cationic clay stabilizer,such as CLAY MASTER 5C from BJ Services, may be first applied to theexterior surface of a porous ceramic material to inhibit penetration bycoating/penetrating material, such as epoxy or resin described elsewhereherein.

[0064] In a selectively configured porous particulate material, theporous particulate material is chemically treated in order to impartdesired physical properties, such as porosity, permeability, apparentdensity or apparent specific gravity, or combinations thereof to theparticulate materials. Such desired physical properties are distinctfrom the physical properties of the porous particulate materials priorto treatment.

[0065] The desired physical properties may further be present innon-selectively configured porous particulate materials. Non-selectivelyconfigured porous particulate materials shall include naturallyoccurring porous ceramic materials as well as non-natural (synthetic)materials manufactured in a manner that renders such desiredcharacteristics.

[0066] The non-selectively configured particulate material is selectedbased on desired physical properties, such as porosity, permeability,apparent density, particle size, chemical resistance or combinationsthereof.

[0067] The selectively configured porous particulate material as well asnon-selectively configured porous particulate material exhibit crushresistance under conditions as high as 10,000 psi closure stress, API RP56 or API RP 60, generally between from about 250 to about 8,000 psiclosure stress, in combination with a apparent specific gravity lessthan or equal to 2.4, to meet the pumping and/or downhole formationconditions of a particular application, such as hydraulic fracturingtreatment, sand control treatment.

[0068] Such desired physical properties may be imparted to a portion orportions of the porous particulate material of the selectivelyconfigured porous particulate material or non-selectively configuredporous particulate material, such as on the particle surface of thematerial particulate, at or in the particle surface of the particulatematerial, in an area near the particle surface of a particulatematerial, in the interior particle matrix of a particulate material or aportion thereof, combinations thereof, etc.

[0069] Advantageously, in one embodiment the low apparent specificgravity of the porous particulate material of the selectively configuredporous particulate material or non-selectively configured porousparticulate material may be taken advantage of to result in a largerfracture or frac pack width for the same loading, such as pound persquare foot of proppant, to give much larger total volume and increasedwidth for the same mass. Alternatively, this characteristic allows forsmaller loading of proppant material to be pumped while still achievingan equivalent width.

[0070] In a preferred embodiment, selective configuration, such as byusing glaze-forming, coating and/or penetrating materials, such as thosematerials described elsewhere herein, may be selectively employed tomodify or customize the apparent specific gravity of a selected porousparticulate material. Modification of particulate apparent specificgravity, to have a greater or lesser apparent specific gravity, may beadvantageously employed, for example, to provide proppant or sandcontrol particulates of customized apparent specific gravity for use asa substantially neutrally buoyant particulate with a variety ofdifferent weight or apparent specific gravity carrier fluids.

[0071] The selectively configured porous particulate material has anapparent density from about 1.1 g/cm³ to about 2.6 g/cm³, a bulkapparent density from about 1.03 g/cm³ to about 1.5 g/cm³, and aninternal porosity from about 10 to about 75 volume percent. In oneexample, bulk densities may be controlled to be in the range of fromabout 1.1 g/cm³ to about 1.5 g/cm³, although greater and lesser valuesare also possible.

[0072] The selectively configured porous particulate material, as wellas the non-selectively configured particulate material, is generallybetween from about 200 mesh to about 8 mesh.

[0073] The selectively configured porous particulate material maycomprise porous particulate material selectively altered by treatingwith a coating or penetrating material using any suitable wet or dryprocess. Methods for coating particulates, such as fracture proppantparticles, with materials such as resin are known in the art, and suchmaterials are available, for example, from manufacturers listed herein.With regard to coating of the disclosed porous particulate materials,coating operations may be performed using any suitable methods known inthe art.

[0074] As used herein, the term “penetration” shall further refer topartially or completely impregnated with a penetrating material, by forexample, vacuum and/or pressure impregnation. For example, porousparticulate material may be immersed in a second material and thenexposed to pressure and/or vacuum to at least partially penetrate orimpregnate the material.

[0075] Those of skill in the art will understand that one or morecoating and/or penetrating materials may be selected to treat a porousmaterial particulate to meet particular criteria or requirements ofgiven downhole application based on the information and examplesdisclosed herein, as well as knowledge in the art. In this regard,porous material particle characteristics, such as composition, porosityand permeability characteristics of the particulate material, size,and/or coating or penetrating material characteristics, such ascomposition, amount, thickness or degree of penetration, may be soselected. The coating or penetrating material is typically non-porous.

[0076] The porosity and permeability characteristics of the porousparticulate material allows the penetrating material to be drawn atleast partially into the porous matrix of the porous particulatematerial by capillary action, for example, in a manner similar to asponge soaking up water. Alternatively, one or more penetratingmaterials may be drawn at least partially into the porous matrix of theporous particulate material using a vacuum, and/or may be forced atleast partially into the porous matrix under pressure.

[0077] Examples of penetrating materials that may be selected for useinclude, but are not limited to, liquid resins, plastics, cements,sealants, binders or any other material suitable for at least partiallypenetrating the porous matrix of the selected particle to providedesired characteristics of strength/crush resistance, apparent specificgravity, etc. It will be understood that selected combinations of anytwo or more such penetrating materials may also be employed, either inmixture or in sequential penetrating applications.

[0078] Examples of resins that may be employed as penetrating and/orcoating materials include, but are not limited to, resins and/orplastics or any other suitable cement, sealant or binder that onceplaced at least partially within a selected particle may be crosslinkedand/or cured to form a rigid or substantially rigid material within theporous structure of the particle. Specific examples of plastics include,but are not limited to, nylon, polyethylene, styrene, etc. andcombinations thereof. Suitable resins include phenol formaldehyderesins, melamine formaldehyde resins, and urethane resins, low volatileurethane resins, such as these and other types of resins available fromBorden Chemical Inc., Santrol, Hepworth of England, epoxy resins andmixtures thereof. Specific examples of suitable resins include, but arenot limited to, resins from Borden Chemical and identified as 500-seriesand 700-series resins (e.g., 569 C, 794 C, etc.). Further specificexamples of resins include, but are not limited to, SIGMASET series lowtemperature curing urethane resins from Borden Chemical, such asSIGMASET, SIGMASET LV, SIGMASET XL, ALPHASET phenolic resin from BordenChemical, OPTI-PROP phenolic resin from Santrol, and POLAR PROP lowtemperature curing resin from Santrol. Where desired, curingcharacteristics, such as curing time, may be adjusted to fit particulartreatment methods and/or final product specifications by, for example,adjusting relative amounts of resin components. Still further examplesof suitable resins and coating methods include, but are not limited to,those found in European Patent Application EP 0 771 935 A1; and in U.S.Pat. Nos. 4,869,960; 4,664,819; 4,518,039; 3,929,191; 3,659,651; and5,422,183, each of the foregoing references being incorporated herein byreference in its entirety.

[0079] In one exemplary embodiment, a curable phenolic resin or othersuitable curable material may be selected and applied as a coatingmaterial so that individual coated particles may be bonded togetherunder downhole temperature, after the resin flows and crosslinks/curesdownhole, such as to facilitate proppant pack/sand control particulateconsolidation after placement.

[0080] Alternatively, a cured phenolic type resin coat or other suitablecured material may be selected to contribute additional strength to theparticles and/or reduce in situ fines migration once placed in asubterranean formation. The degree of penetration of the coating orpenetrating fluid into the porous particulate material may be limited bydisconnected porosity, such as substantially impermeable or isolatedporosity, within the interior matrix of the particulate.

[0081] This may either limit the extent of uniform penetration ofpenetrating material in a uniform manner toward the core, such asleaving a stratified particle cross section having outside penetratinglayer with unpenetrated substantially spherical core, and/or may causeuneven penetration all the way to the core, such as bypassing “islands”of disconnected porosity but penetrating all the way to the core. In anyevent, a penetrating and/or coating material may trap or encapsulate air(or other fluid having apparent specific gravity less than particlematrix and less than coating/penetrating material) within thedisconnected porosity in order to reduce apparent specific gravity bythe desired amount. Such materials coat and/or penetrate the porousparticulate without invading the porosity to effectively encapsulate theair within the porosity of the particle. Encapsulation of the airprovides preservation of the ultra-lightweight character of theparticles once placed in the transport fluid. If the resin coating ortransport fluids were to significantly penetrate the porosity of theparticle, the density increases accordingly, and the particle no longerhas the same lightweight properties. The resin coat also adds strengthand substantially enhances the proppant pack permeability at elevatedstress.

[0082] Coating layers may be applied as desired to contribute toparticle strength and/or reduce in situ fines migration once placed in asubterranean formation. The coating significantly increases the strengthand crush resistance of the ultra-lightweight ceramic particle. In thecase of natural sands the resin coat protects the particle fromcrushing, helps resist embedment, and prevents the liberation of fines.

[0083] The coating or penetrating fluid is typically selected to have anapparent specific gravity less than the apparent specific gravity of theporous particulate material so that once penetrated at least partiallyinto the pores of the matrix it results in a particle having a apparentspecific gravity less than that of the porous particulate material priorto coating or penetration, i.e., filling the pore spaces of a porousparticulate material results in a solid or substantially solid particlehaving a much reduced apparent density.

[0084] For example, the selected porous particulate material may betreated with a selected penetrating material in such a way that theresultant selectively configured porous particulate material has a muchreduced apparent density, such as having a apparent density closer to orapproaching the apparent specific gravity of a carrier fluid so that itis neutrally buoyant or semi-buoyant in a fracturing fluid or sandcontrol fluid.

[0085] Alternatively, a penetrating material may be selected so that ithelps structurally support the matrix of the porous particulate material(i.e., increases the strength of the porous matrix) and increases theability of the particulate to withstand the closure stresses of ahydraulic fractured formation, or other downhole stresses.

[0086] For example, a penetrating material may be selected by balancingthe need for low apparent density versus the desire for strength, i.e.,a more dense material may provide much greater strength. In this regard,the inherent and/or induced porosity of the porous particulate materialmay be selected so as to help provide the desired balance betweenapparent density and strength. It will be understood that othervariable, such as downhole temperature and/or fluid conditions, may alsoimpact the choice of penetrating materials.

[0087] The coating layer or penetrating material is generally present inthe selectively configured porous particulate material in an amount offrom about 0.5% to about 10% by weight of total weight. The thickness ofthe coating layer of the selectively configured porous particulatematerial is generally between from about 1 to about 5 microns. Theextent of penetration of the penetrating material of the selectivelyconfigured porous particulate material is from less than about 1%penetration by volume to less than about 25% penetration by volume.

[0088] Especially preferred results are obtained when the porousparticulate material is a porous ceramic particle having an apparentdensity of 1.25 or less and untreated porosity is approximately 60%.Such materials may be treated with a coating material that does notpenetrate the porous matrix of the porous particulate material, or thatonly partially penetrates the porous matrix of the ceramic particulatematerial. Such treated ceramic materials may have an apparent densityfrom about 1.1 g/cm³ to about 1.8 g/cm³ (alternatively from about 1.75g/cm³ to about 2 g/cm³ and further alternatively about 1.9 g/cm³), abulk apparent density from about 1.03 g/cm³ to about 1.5 g/cm³, and atreated internal porosity from about 45% to about 55%. However, valuesoutside these exemplary ranges are also possible.

[0089] As an example, a porous ceramic treated with about 6% epoxy hasbeen seen to exhibit a bulk apparent density of about 1.29 and aporosity of about 50.6%, a porous ceramic treated with about 8% epoxyexhibits a bulk apparent density of about 1.34 and a porosity of about46.9%, a porous ceramic treated with about 6% phenol formaldehyde resinexhibits a bulk apparent density of about 1.32 and a porosity of about51.8%, and a porous ceramic treated with about 8% phenol formaldehyderesin exhibits a bulk apparent density of about 1.20 and a porosity ofabout 54.1%.

[0090] In this embodiment, a coating material or penetrating materialmay be selected to be present in an amount of from about 0.5% to about10% by weight of total weight of individual particles. When present,thickness of a coating material may be selected to be from about 1 toabout 5 microns on the exterior of a particle. When present, extent ofpenetration penetrating material into a porous material particle may beselected to be from less than about 1% penetration by volume to lessthan about 25% penetration by volume of the particle. It will beunderstood that coating amounts, coating thickness, and penetrationamounts may be outside these exemplary ranges as well.

[0091] Further, the porous particulate material may be at leastpartially selectively configured by glazing, such as, for example,surface glazing with one or more selected non-porous glaze materials. Insuch a case, the glaze, like the coating or penetrating material, mayextend or penetrate at least partially into the porous matrix of theporous particulate material, depending on the glazing method employedand/or the permeability (i.e., connectivity of internal porosity)characteristics of the selected porous particulate material, such asnon-connected porosity allowing substantially no penetration to occur.For example, a selected porous particulate material may be selectivelyconfigured, such as glazed and/or coated with a non-porous material, ina manner so that the porous matrix of the resulting particle is at leastpartially or completely filled with air or some other gas, i.e., theinterior of the resulting particle includes only air/gas and thestructural material forming and surrounding the pores. Once again, theinherent and/or induced porosity of a porous material particle may beselected so as to help provide the desired balance between apparentdensity and strength, and glazing and/or coating with no penetration (orextension of configured area into the particle matrix) may be selectedto result in a particle having all or substantially all porosity of theparticle being unpenetrated and encapsulated to trap air or otherrelatively lightweight fluid so as to achieve minimum apparent specificgravity. In addition to sealing a particle, such as to seal air/gaswithin the porous matrix of the particle, such selective configuration,such as using glazing and/or coating materials, may be selected toprovide other advantages.

[0092] In a preferred embodiment, the porous particulate material, suchas the above-described fired kaolinitic particles, is manufactured byusing a glaze-forming material to form a glaze to seal or otherwisealter the permeability of the particle surface, so that a given particleis less susceptible to invasion or saturation by a well treatment fluidand thus capable of retaining relatively lightweight or substantiallyneutrally buoyant characteristics relative to the well treatment fluidupon exposure to such fluid. Such glazing may be accomplished using anysuitable method for forming a glaze on the surface or in the nearsurface of a particle, including by incorporating a glaze-formingmaterial into the raw material “green paste” that is then formed such asmolded into shape of the particle prior to firing. Those skilled in theart recognize that glazes may be made from a variety of methods,including the application of a smooth, glassy coating such that a hard,nonporous surface is formed. Glazes may be formed from powdered glasswith oxides. The mixture of powders is suspended in water and applied tothe substrate. The glaze can be dried and then fixed onto the substrateby firing or similar process known to those skilled in the art.Additionally, the use of borates or similar additives may improve theglaze.

[0093] Examples of such glaze-forming materials include, but are notlimited to, materials such as magnesium oxide-based material, boricacid/boric oxide-based material, etc. During firing, the glaze-formingmaterial/s “bloom” to the surface of the particles and form a glaze.Alternatively, glazing may be accomplished, for example, by applying asuitable glaze-forming material onto the surface of the formed rawmaterial or “green” particles prior to firing such as by spraying,dipping, and similar methods so that glazing occurs during particlefiring. Further alternatively, a glaze-forming material may be appliedto a fired ceramic particle, and then fired again in a separateglaze-forming step. In one embodiment, the glaze forms a relatively hardand relatively non-porous surface during firing of the particles.

[0094] Advantages of such a glazing treatment include maintaining therelatively low apparent density of a relatively lightweight porousparticle without the necessity of further alteration, such as necessityof coating with a separate polymer coating although optional coatingsmay be applied if so desired. Furthermore, the resulting relativelysmooth glazed surface of such a particle also may serve to enhance theease of multi phase fluid flow, such as flow of water and gas and oil,through a particulate pack, such as through a proppant pack in afracture, resulting in increased fracture conductivity.

[0095] In an alternative embodiment, one or more types of the disclosedselectively configured porous particulate material or non-selectivelyconfigured porous particulate material may be employed as particulatesfor well treating purposes in combination with a variety of differenttypes of well treating fluids (including liquid CO₂-based systems andother liquefied-gas or foamed-gas carrier fluids) and/or other types ofparticulates such as to achieve synergistic benefits, it beingunderstood that benefits of the disclosed methods and compositions mayalso be achieved when employing only one type of the disclosed porousmaterials as a sole well treating particulate. Furthermore, althoughexemplary embodiments are described herein with reference to porousmaterials and to relatively lightweight porous materials, it will beunderstood that benefits of the disclosed methods and compositions mayalso be realized when applied to materials that may be characterized asnon-relatively lightweight and/or non-porous in nature.

[0096] Elimination of the need to formulate a complex suspension gel maymean a reduction in tubing friction pressures, particularly in coiledtubing and in the amount of on-location mixing equipment and/or mixingtime requirements, as well as reduced costs. Furthermore, whenselectively configured, such as by glazing and/or by treating withcoating/penetrating material, to have sufficient strength and relativelightweight properties, the disclosed relatively particles may beemployed to simplify hydraulic fracturing treatments or sand controltreatments performed through coil tubing, by greatly reducing fluidsuspension property requirements. Downhole, a much reduced propensity tosettle (as compared to conventional proppant or sand controlparticulates) may be achieved, particularly in highly deviated orhorizontal wellbore sections. In this regard, the disclosed particulatematerial may be advantageously employed in any deviated well having anangle of deviation of between about 0 degree and about 90 degrees withrespect to the vertical. However, in one embodiment, the disclosedparticulate material may be advantageously employed in horizontal wells,or in deviated wells having an angle with respect to the vertical ofbetween about 30 degrees and about 90 degrees, alternatively betweenabout 75 degrees and about 90 degrees. Thus, use of the disclosedparticulate materials disclosed herein may be employed to achievesurprising and unexpected improvements in fracturing and sand controlmethodology, including reduction in proppant pack and/or formationdamage, and enhancement of well productivity.

[0097] It will be understood that the characteristics of glazingmaterials, penetrating materials and/or coating materials given herein,such as composition, amounts, types, are exemplary only. In this regard,such characteristics may be selected with benefit of this disclosure bythose of skill in the art to meet and withstand anticipated downholeconditions of a given application using methods known in the art, suchas those described herein.

[0098] In another disclosed embodiment, blends of two or more differenttypes of particles having different particulate characteristics, such asdifferent porosity, permeability, apparent density or apparent specificgravity, settling velocity in carrier fluid, may be employed as welltreatment particulates. Such blends may contain at least one porousparticulate material and at least one other particulate material thatmay or may not be a porous particulate material.

[0099] In addition, the selectively configured porous particulatematerial and non-selectively configured porous particulate material maybe used as two or more multiple layers. In this regard, successivelayers of such materials may be employed. For instance, multiple layersmay consist of at least one selectively configured porous particulatematerial and at least one non-selectively configured porous particulatematerial.

[0100] In one exemplary embodiment, a selected coating or penetratingmaterial may be a urethane, such as ethyl carbamate-based resin, appliedin an amount of about 4% by weight of the total weight of the selectedporous material particle. A selected coating material may be applied toachieve a coating layer of at least about 2 microns thick on theexterior of the selected porous material particle.

[0101] Such blends may be further employed in any type of well treatmentapplication, including in any of the well treatment methods describedelsewhere herein. In one exemplary embodiment, such blends may beemployed to optimize hydraulic fracture geometries to achieve enhancedwell productivity, such as to achieve increased propped fracture lengthin relatively “tight” gas formations. Choice of different particulatematerials and amounts thereof to employ in such blends may be made basedon one or more well treatment considerations including, but not limitedto, objective/s of well treatment, such as for sand control and/or forcreation of propped fractures, well treatment fluid characteristics,such as apparent specific gravity and/or rheology of carrier fluid, welland formation conditions such as depth of formation, formationporosity/permeability, formation closure stress, type of optimizationdesired for geometry of downhole-placed particulates such as optimizedfracture pack propped length, optimized sand control pack height,optimized fracture pack and/or sand control pack conductivity andcombinations thereof.

[0102] Such different types of particles may be selected, for example,to achieve a blend of different specific gravities or densities relativeto the selected carrier fluid. For example, a blend of three differentparticles may be selected for use in a water fracture treatment to forma blend of well treatment particulates having three different specificgravities, such as apparent specific gravity of first type of particlefrom about 1 to less about 1.5; apparent specific gravity of second typeof particle from greater than about 1.5 to about 2.0; and apparentspecific gravity of third type of particle from about greater than about2.0 to about 3.0; or in one specific embodiment the three types ofparticles having respective specific gravities of about 2.65, about 1.7and about 1.2, it being understood that the preceding apparent specificgravity values are exemplary only and that other specific gravities andranges of specific gravities may be employed. In one example, at leastone of the types of selected well treatment particulates may be selectedto be substantially neutrally buoyant in the selected carrier fluid.

[0103] Such different types of particles may be selected for use in anyamount suitable for achieving desired well treatment results and/orcosts. However, in one embodiment multiple types of particles may beselected for use in a blend of well treatment particulates in amountsthat are about equal in proportion on the basis of total weight of theblend. Thus, three different types of particles may each be employed inrespective amounts of about ⅓ of the total blend such as by total weightof the blend, four different types of particles may each be employed inrespective amounts of about ¼ of the total blend such as by total weightor the blend. However, these relative amounts are exemplary only, itbeing understood that any desired relative amount of each selected typeof well particulate may be employed, such as for one exemplaryembodiment of blend having three different types of particles, such asselected from the different types of particles described elsewhereherein, the amounts of each selected type of particle may be present inthe blend in an amount ranging from about 10% to about 40% such as bytotal weight of the blend to achieve 100% weight of the total blend.

[0104] It will be understood with benefit of this disclosure that choiceof different particulate materials and amounts thereof to employ in suchblends may be made using any methodology suitable for evaluating suchblends in view of one or more desired well treatment considerations. Inone embodiment, any method known in the art suitable for modeling orpredicting sand control pack or fracture pack geometry/conductivity maybe employed, such as illustrated and described in relation to Example 4herein.

[0105] Examples of different particle types which may be selected foruse in such blends include, but are not limited to, conventional sandparticulates, such as Ottawa sand, relatively lightweight well treatmentparticulates, such as ground or crushed nut shells at least partiallysurrounded by at least one layer component of protective or hardeningcoating, selectively configured porous materials, such as any one ormore of the selectively configured porous materials described herein,such as deformable particles. Further examples of particle types whichmay be selected for use in such blends include any of those particlesdescribed in U.S. patent application Ser. No. 10/113,844, filed Apr. 1,2002; U.S. patent application Ser. No. 09/579,146, filed May 25, 2000;U.S. Pat. No. 6,364,018; U.S. Pat. No. 6,330,916; and U.S. Pat. No.6,059,034, each of which is incorporated herein by reference.

[0106] In one exemplary embodiment, selected blends of conventional sandproppant, relatively lightweight particulates of ground or crushed nutshells at least partially surrounded by at least one layer component ofprotective or hardening coating, and selectively configured porousmaterials such as relatively lightweight porous material firedkaolinitic particles treated with a penetrating/coating materialsdescribed herein may be employed in a hydraulic fracture treatmentutilizing ungelled or weakly gelled carrier fluid. One specific exampleof such a blend is described in Example 4 herein. In such an embodiment,these different types of particles may be employed in any relativevolume or weight amount or ratio suitable for achieving desired welltreatment results.

[0107] In one specific example, these different types of particles maybe employed in a well treatment particulate composition including about⅓ by weight of conventional sand proppant by total weight of welltreatment particulate, about {fraction (1/3)} by weight of relativelylightweight particulate, such as core of ground or crushed nut shells atleast partially surrounded by at least one layer component of protectiveor hardening coating) by total weight of well treatment particulate, andabout ⅓ by weight of selectively configured relatively lightweightporous material, such as fired kaolinitic particles treated with apenetrating/coating materials described herein, by total weight of welltreatment particulate. It will be understood that the foregoing relativeamounts are exemplary only and may be varied, for example, to achievedesired results and/or to meet cost objectives of a given treatment. Itwill also be understood that the disclosed methods and compositions mayalso be practiced with such blends using other types of relativelylightweight particulate materials as described elsewhere herein, such asporous polymeric materials, such as polyolefins, styrene-divinylbenzenebased materials, polyalkylacrylate esters and modified starches.Further, any of the disclosed porous materials may be employed in “neat”or non-altered form in the disclosed blends where apparent density andother characteristics of the particle are suitable to meet requirementsof the given well treating application.

[0108] In one respect, disclosed are well treating methods, such ashydraulic fracturing and sand control, which may be employed to treat awell penetrating a subterranean formation, and include introducing intoa well a selected porous particulate material that is treated with aselected coating material, selected penetrating material, or combinationthereof. Individual particles of the particulate material optionally mayhave a shape with a maximum length-based aspect ratio of equal to orless than about 5. In one embodiment porous particulate materials may beany particulate material with suitable internal porosity and/orpermeability characteristics to achieve the desired finished particleproperties when combined with selected penetrating/coating materials asdescribed elsewhere herein.

[0109] Examples of suitable porous material particulates that may beselected for use in aqueous based carrier fluids include, but are notlimited to porous ceramics, porous polymeric materials or any otherporous material or combinations thereof suitable for selection forcombination of internal porosity and permeability to achieve desiredproperties, such as strength and/or apparent specific gravity, forparticular downhole conditions and/or well treatment applications asdescribed elsewhere herein. For example, porous ceramic particles may bemanufactured by firing at relatively low temperatures to avoid loss ofporosity due to crystallization and driving off of water. Particularexamples include, but are not limited to, porous ceramic particlesavailable from Carbo Ceramics Inc. of Irving, Tex. composed of firedkaolinitic clay that is fired at relatively low temperature of about1235° F. or about 1300° F. (or about 700° C. and that has trace amountsof components such as cristobalite, mullite and opalite), polyolefinparticles, and similar components.

[0110] In another disclosed embodiment, relatively lightweightparticulates or blends including such particulates as describedelsewhere herein, such as including selectively configured particulatesand/or non-selectively configured particulates described elsewhereherein, may be advantageously employed as well treatment particulates,such as fracture proppant particulate or sand control particulate, inliquefied gas and foamed gas carrier fluids.

[0111] Examples of types of such carrier fluids include, but are notlimited to, liquid CO₂-based systems, liquid CO₂, CO₂/N₂, and foamed N₂in CO₂ systems that may be employed in hydraulic fracturingapplications. In one specific embodiment, porous ceramic wellparticulates having a bulk apparent density of close to or about 1.0g/cm³, in either selectively configured or non-selectively configuredform, may be employed with such liquefied gas and/or foamed gas carrierfluids, such as liquid CO₂-based systems, liquid CO₂, CO₂/N₂, and foamedN₂ in CO₂ systems. In another specific embodiment, selectivelyconfigured particulates and/or non-selectively configured particulatesmay be employed that may be characterized as substantially neutrallybuoyant in such liquefied gas and/or foamed gas carrier fluids.

[0112] Liquid CO₂ has a density close to about 1.02 g/cm³ under typicalfracturing conditions, and conventional proppants, such as sand, ornon-relatively lightweight ceramic proppants have a tendency to settlein liquid CO₂-based systems. Furthermore, liquid CO₂ has very little ifany viscosity, and therefore proppant transport in a liquid CO₂-basedsystem is provided by turbulence and frictional forces, and fracturescreated by liquid CO₂ are typically relatively narrow. Advantageously,using the disclosed methods and compositions, proppant transport ofrelatively lightweight particulates is easier than is proppant transportof conventional sand proppants or non-relatively lightweight ceramicproppants.

[0113] In one exemplary embodiment, relatively lightweight porousceramic particles may be employed in liquid CO₂-based systems. Examplesof types of such relatively lightweight porous ceramic particlesinclude, but are not limited to, those porous ceramic particlesavailable from Carbo Ceramics for controlled release applicationsaltered in the manufacturing process to have a bulk apparent densityclose to about 1.0 g/cm³. Other suitable examples of relativelylightweight porous particles include, but are not limited to, thoseparticles having a bulk apparent density of less than about 2.5 g/cm³,alternatively having a bulk apparent density of from about 1.0 to about2.0 g/cm³, further alternatively having a bulk apparent density of fromabout 1.2 g/cm³ to about 2.0 g/cm³.

[0114] One specific example of suitable relatively lightweight porousceramic particle for use in CO₂-based systems of this embodiment isporous ceramic material described elsewhere herein, either inselectively configured form, as described herein in Example 1, or innon-selectively configured or non-altered or “neat” form.

[0115] In one exemplary embodiment, the practice of the disclosedmethods and compositions, relatively lightweight porous ceramicmaterials or blends thereof may be employed as fracture proppantmaterials in liquid CO₂-based fracturing systems using methodologiessimilar or the same to those employed with conventional proppants inliquid CO₂-based fracturing systems. In this regard, liquid CO₂-basedfracturing job characteristics, such as proppant amounts, proppantsizes, mixing and pumping methodologies, using relatively lightweightporous ceramic materials may be the same as described for conventionalproppants in “The History and Success of Liquid CO₂ and CO₂/N₂Fracturing System” by Gupta and Bobier, SPE 40016, March 1998. Furtherinformation on liquid CO₂-based fracturing job characteristics that maybe employed with relatively lightweight porous ceramic materials may befound in U.S. Pat. No. 4,374,545, U.S. Pat. No. 5,558,160, U.S. Pat. No.5,883,053, Canadian Patent No. 2,257,028 and Canadian Patent No.2,255,413, each of the foregoing references being incorporated herein byreference.

[0116] In one disclosed exemplary embodiment, relatively lightweightporous ceramic particles employed as fracture proppant particulate in aliquid CO₂-based system may be used in “neat” or non-altered form andmay have a apparent specific gravity of from about 1.17 to about 2.0 Inanother disclosed exemplary embodiment, using relatively lightweightporous ceramic particles as fracture proppant particulate in a liquidCO₂-based system allows the concentration of proppant in such a systemto be advantageously extended to about 1200 Kg/cubic meter. Otheradvantages of using the disclosed relatively lightweight porous ceramicparticles in liquid CO₂-based fracturing systems include, but are notlimited to, reduced proppant settling in surface mixing equipment priorto pumping downhole and improved proppant transport downhole and intothe formation. It will be understood that although described above forembodiments employing relatively lightweight porous ceramic particles,the disclosed methods and compositions may also be practiced with liquidCO₂-based systems using other relatively lightweight porous materialparticulate materials and blends thereof described elsewhere herein,such as porous polymeric materials such as polyolefins. Any of suchmaterials may be employed in “neat” or non-altered form with liquidCO₂-based systems where apparent density and other characteristics ofthe particle are suitable to meet requirements of the given welltreating application, or may alternatively be employed in selectivelyconfigured form as described elsewhere herein.

[0117] The following examples will illustrate the practice of thepresent invention in a preferred embodiment. Other embodiments withinthe scope of the claims herein will be apparent to one skilled in theart from consideration of the specification and practice of theinvention as disclosed herein. It is intended that the specification,together with the example, be considered exemplary only, with the scopeand spirit of the invention being indicated by the claims which follow.

EXAMPLES

[0118] The following examples are illustrative and should not beconstrued as limiting the scope of the invention or claims thereof.

Example 1

[0119] To obtain the data for this example, the following procedure wasfollowed: Measured mass of 25 ml of sample on a graduate cylinder.Cylinder was tapped several times on the countertop and the volumeadjusted to an even 25 ml prior to weighing.

[0120] Mass/volume=bulk density.

[0121] The data of this example is shown in Table 1: TABLE 1 BulkDensities Sand 1.721 CarboLite 1.747 Porous Ceramic-Neat 1.191 PorousCeramic-2/2 1.238 Porous Ceramic-6% 1.293 Porous Ceramic-8% P-A 1.224Porous Ceramic-8% P-B 1.198 Porous Ceramic-10% P 1.32

[0122]FIG. 1 illustrates comparisons of the bulk densities of variousproppants/sand control materials to samples of a selected porous ceramicmaterial (from Carbo Ceramics, Inc.).

[0123] In the examples, “Carbolite” is a commercial proppant availablefrom Carbo Ceramics, Inc. “Neat” is untreated porous ceramic materialfrom Carbo Ceramics, Inc., “{fraction (2/2)}” is porous ceramic materialfrom Carbo Ceramics, Inc. treated with 2% by weight of particle epoxyinner coating/penetrating material (epoxy is reaction product ofepichlorohydrin and bis-phenol A) and with 2% by weight of particlephenol formaldehyde resin outer coating material, “6%” is porous ceramicmaterial from Carbo Ceramics, Inc. treated with 6% by weight of particlecoating/penetrating material (epoxy is reaction product ofepichlorhidian and bis-phenol A), “8% P-A” is porous ceramic materialfrom Carbo Ceramics, Inc. treated with 8% by weight of particle phenolformaldehyde resin (Sample A), “8% P-B” is porous ceramic material fromCarbo Ceramics, Inc. treated with 8% by weight of particle phenolformaldehyde resin (Sample B), and “10% P” is porous ceramic materialfrom Carbo Ceramics, Inc. treated with 10% by weight of particle phenolformaldehyde resin.

[0124] Data is presented for both the untreated porous materialparticle, and for the porous material particle treated with varioustypes and concentrations of selected penetrating materials. As may beseen, the bulk apparent density of the resulting particles varies withvarying degree of infiltration or penetration of the penetratingmaterial into the porous ceramic particle. The samples designated as{fraction (2/2)} and 8% P-B may be characterized from SEM thin sectionanalysis as having limited penetration towards the core of the particle,apparent effective encapsulation of the air in the particle coreporosity, yet substantial enhancement of the particle strength asillustrated by the conductivity tests.

[0125]FIGS. 2 and 5 illustrate the permeability versus closure stressfor coated and uncoated ceramic ULW particulates. As shown, resincoating and impregnation of the ULW particle imparts significantstrength across the closure range and in particular, enhances the low tomid-range performance of the material. The data represents equal packwidths for all of the proppants with adjustments made for eachrespective density. Both the coated and uncoated ceramics ULW weretested at 1.4 pounds per square foot (33.2 kg/m²). Each of these testshad nearly identical width measurements for ease of comparison.

Example 2

[0126] The porous particulate material employed was from “CarboCeramics” having a size of about 20/40 mesh. The particulate materialwas treated with various penetrating/coating materials corresponding tothe same epoxy or phenol formaldehyde materials used above. The treatedparticulate material was tested alone, with no other particulatematerial blended in. Comparison materials include Jordan Sand,“Econoprop” proppant from Carbo Ceramics, “Econoflex” (coated Econopropproppant), Hickory sand (Brady Sand), “PR6000” 2% coated Ottawa sandfrom BORDEN, and “Carbolite” proppant from Carbo Ceramics.

[0127] Conductivity tests were performed according to API RP 61 (1^(st)Revision, Oct. 1, 1989) using an API conductivity cell with Ohiosandstone wafer side inserts. Each particulate material sample wasloaded into the cell and closure stress applied to the particulatematerial using a “DAKE” hydraulic press having a “ROSEMOUNT”differential transducer (#3051C) and controlled by a “CAMILE”controller. Also employed in the testing was a “CONSTAMETRIC 3200”constant rate pump which was used to flow deionized water through eachparticulate sample.

[0128] Table 2 shows the proppant pack Permeability and Conductivitydata generated for this example. TABLE 2 Porous Ceramic Worksheet PC-PC- PC- PC- PC- PC- PC- PC 4% 6% 8% 2% 6% 8% 10% 20/40 20/40 20/40 20/4020/40 20/40 neat Epoxy epoxy epoxy &2% resin resin resin JordanEconoprop Econoflex Hickory PR 6000 Carbolite Bulk Dens 1.198 1.292 1.341.238 1.293 1.224 1.32 1.6 1.6 1.5 1.6 1.54 1.6 Acid 5.7% 1.20% 1.90%0.30% 0.50% 0.30% 1.70% Solubility Porosity 50.2% 46.9% 51.8% 54.1%Crush 2000 3.65 .1 0.4 0.1 3000 .3 1.8 0.2 4000 7.52 4.54 1.6 0.1 9.80.4 5000 2.6 13.6 0.7 6000 16.88 16.36 0.1 1.9 7000 21.00 7500 4.7 3.11.5 8000 20.87 0.2 4.5 10000  13.3 0.5 10.7 12.1 Permeability 2000 149425 322 409 406 559 1193 508 228 342 287 224 275 500 3000 110 331 226304 318 376 994 384 170 319 274 144 241 466 4000 70 237 130 190 230 192786 260 113 295 262 64 208 433 5000 97 110 131 185 151 671 181 80 257255 42 168 376 6000 64 89 142 110 546 101 47 220 248 21 127 319 7000 4855 78 361 32 178 225 12 94 252 8000 28 44 46 175 18 135 202 4 61 186Conductivity 2000 2726 8436 4693 5965 5484 4658 13522 5760 2116 34232586 2020 2550 4755 3000 1915 5152 3194 4283 4053 3177 10275 4116 15643132 2382 1276 2201 4383 4000 1103 1868 1695 2600 2621 1695 7028 24721013 2842 2178 532 1852 4011 5000 949 1356 1616 1983 1221 5406 1729 7092442 2036 344 1468 3445 6000 747 1042 1345 747 3783 986 405 2042 1895157 1085 2879 7000 526 604 522 2455 279 1621 1650 94 790 2255 8000 296463 296 1127 154 1201 1405 31 495 1637

[0129] Data is presented graphically in FIGS. 2-6.

[0130] Conductivity is a function of the width times the permeability.Advantageously, as disclosed herein in one embodiment, a selected porousmaterial particulate may be treated with a selected coating and/orpenetrating material to produce a relatively lightweight particulatesample that at the same 1 b/sq ft loading as a conventional sand willoccupy a greater width. Even if the pack permeability is the same, theconductivity, and thus the proppant pack producability, will be higher.Thus, as represented by the conductivity data, the benefit of thecombination of increased width and the improved permeability may beachieved. Further, as disclosed herein in one embodiment, a selectedporous material particulate may be treated with a selected coatingand/or penetrating material so that particle strength is maintained toas high a confining (or closure) stress as possible, which is reflectedmore directly by the permeability data. Thus a certain amount offracture conductivity at a given stress/temp condition may be maintainedwithout increasing the cost, and/or by offsetting any cost increase withimproved value. Even in the event of increased particulate materialcost, substantially less particulate material may be employed to achievea substantially equivalent conductivity due to the lesser mass/unitvolume.

Example 3

[0131] Using the selected treated material of the Examples above,particles may be produced that are capable for use, such as havingsufficient crush resistance for use or do not crush, under conditions of2000 psi closure stress or greater, alternatively 2500 psi closurestress or greater, alternatively 3000 psi closure stress or greater,alternatively up to at least about 6000 psi closure stress,alternatively up to at least about 7000 psi closure stress, andalternatively at least about 8000 psi closure stress, i.e., almost asresistant to crush as commercial ceramic proppants which are heavier(e.g., commercial ceramic proppant (CarboLite) is about 40% heavier). Inanother embodiment, particles may be produced that are capable for use(e.g., have sufficient crush resistance for use or do not crush) underconditions of from about 2000 psi closure stress to about 8000 psiclosure stress, alternatively from about 2500 psi closure stress toabout 8000 psi closure stress, alternatively from about 3000 psi closurestress to about 8000 psi closure stress. However, it will be understoodthat particles may produced that are capable of use at higher closurestresses than 8000 psi and lower closure stresses than about 2000 psi aswell.

[0132]FIGS. 8-15 are cross-sectional and surface SEM photographs ofvarious treated and untreated samples of porous ceramic materials fromCARBO CERAMICS. Where indicated as “epoxy” or as “resin”, the particularcoating/penetrating material is either the same epoxy or phenolformaldehyde resin employed and identified in Example 1.

[0133]FIG. 8 shows particles treated with about 10% by weight ofparticle resin. FIG. 9 shows particles treated first with 2% by weightepoxy and second with 2% by weight resin. FIG. 10 shows untreatedparticles. FIG. 11 shows particles treated first with 2% by weight epoxyand second with 2% by weight resin. FIG. 12 shows surface of untreatedparticle. FIG. 13 shows untreated particles. FIG. 14 shows particlestreated with 8% by weight epoxy. FIG. 15 shows particles treated with 6%by weight epoxy.

Example 4

[0134] In this example, a selected blend of three different apparentspecific gravity well treatment particulates were evaluated for use in awater fracture treatment of a “tight” gas well based on a Canyon Sandgas well. The three different apparent specific gravity particulateswere chosen to represent, for example, a selected blend of the followingdifferent types of well treatment particulates:

[0135] I. 20/40 mesh Ottawa sand having the following properties:apparent specific gravity of 2.65; Vt=17.5 ft/min @ Nre=+/−500 (Typicalfor water fracs)

[0136] II. 20/40 mesh porous ceramic particles coated with 2% resin(described elsewhere herein) having the following properties: apparentspecific gravity of 1.70; Vt=9.5 ft/min @ Nre=+/−500 (Typical for waterfracs)

[0137] III. 20/40 mesh ground or crushed nut shells coated withprotective or hardening coating (e.g., “LiteProp” from BJ Servicesdescribed in U.S. Pat. No. 6,364,018 and U.S. patent application Ser.No. 09/579,146, each incorporated herein by reference) having thefollowing properties: apparent specific gravity of 1.20; Vt=3.9 ft/min @Nre=+/−500 (Typical for water fracs)

[0138] As may be seen from the data above, particulate III weighs abouthalf as much as Particulate I, but settles at a rate less than about ¼as fast.

[0139] A well treatment particulate including a selected blend ofroughly equal amounts of the above types of particulates (i.e., about ⅓by weight of above particulate I of the total weight of the blend, about{fraction (1/3)} by weight of above particulate II of the total weightof the blend, and about ⅓ by weight of above particulate III of thetotal weight of the blend) was modeled for use in a water fracturetreatment of a “tight” gas well using a hydraulic fracture simulationprogram. FIG. 16 illustrates proppant distribution in the resultingsimulated hydraulic fracture created downhole.

[0140] For comparison purpose, a well treatment particulate includingonly particulate I (Ottawa sand) was modeled for use in a water fracturetreatment of the same “tight” gas well similarly modeled using the samepumping schedule (but in this case using 135,000 pounds of Ottawa sand).FIG. 17 illustrates proppant distribution in the resulting simulatedhydraulic fracture created downhole.

[0141] As may be seen from a comparison of the resulting proppedprofiles of FIGS. 16 and 17, the well treatment particulate includingonly particulate I (Ottawa sand) resulted in a proppant distributionthat propped the bottom half of the pay out to about 1000′ (see FIG.18), while the well treatment particulate including a selected blend ofroughly equal amounts of particulates I, II and III resulted in asynergistic proppant distribution that propped all of the pay out toalmost 2000′ (see FIG. 16), or approximately four times the proppedfracture surface area.

Example 5

[0142] The proppant distributions of FIG. 16 and FIG. 17 were next inputinto a reservoir production simulator (“M-Prod”) and gas productionseparately simulated for each proppant distribution. An assumption wasmade that the effective conductivity of the proppant distribution ofFIG. 16 (i.e., roughly equal amounts of particulates I, II and III)would have only 1/10^(th) the effective conductivity of the proppantdistribution of FIG. 17 (i.e., particulate I only). The proppantdistribution of FIG. 17 (i.e., particulate I only) produced at aninitial potential of 707 MCFD with a cumulative production of 595 MMCFover ten years, while the proppant distribution of FIG. 16 (i.e.,roughly equal amounts of particulates I, II and III) produced at aninitial potential of 920 mcf/day (“MCFD”) with a cumulative productionof 1312 MMCF over ten years. Thus, the -proppant distribution of FIG. 16(i.e., roughly equal amounts of particulates I, II and III) resulted inthe production of twice the reserves from the same well as the proppantdistribution of FIG. 17 (i.e., particulate I only), despite having only1/10^(th) of assumed conductivity. This shows how the disclosed selectedblend of different types of well treatment particulates may beadvantageously employed to achieve increased production rates andreserves from relatively tight gas formations by increasing proppedfracture lengths, even with reduced effective conductivities.

[0143] Although this example illustrates the use of a selected blend ofdifferent types and amounts of well treatment particulates in a tightgas well, it will be understood that blends of these and other types ofwell treatment blends may be selected and employed for other types ofwells, including wells productive of liquids as well as gas, and wellshaving relatively higher formation permeability values. Furthermore, itwill be understood that benefits of the disclosed method may be realizedusing blends of other than three different types of well treatmentparticulates, for example, using two different types of well treatmentparticulates or more than three different types of well treatmentparticulates (e.g., as many as four, five, six, seven, eight, nine andmore different types of well treatment particulates) having varyingcharacteristics.

Example 6

[0144] ULW-1.75 corresponds to 2/2 discussed above in Example 1 and canbe characterized as a porous ceramic particle with the roundness andsphericity common to ceramic proppants. The porosity averages 50%,yielding a bulk density of 1.10 to 1.15 g/cm³. Median-sized 20/40particles of the ULW-1.75 and Ottawa sand were used. The 20/40 Ottawasand has an average bulk density of 1.62 g/cm with a specific gravity of2.65. The ULW-1.75 has a bulk density of 1.05 to 1.10.

[0145] Static particle settling evaluations were conducted in freshwater to determine the differences in settling rate between theconventional proppant and the ULW particles. Median sized 20/40particles of each proppant were used for the evaluations. Stokes Lawcalculations giving the fall velocity in ft/minute are presented inTable 3 and were calculated as:

V=1.15×10³(d _(prop) ²/μ_(fluid))(Sp.Gr. _(Prop) −Sp.Gr. _(fluid))

[0146] where velocity is in ft/min., diameter d is the average particlediameter and, μis fluid viscosity in cps. TABLE 3 Static Settling Ratesfor Proppants as Derived by Stoke's Law 20/40 Proppant Sp.Gr. SettlingVelocity ft/minute Ottawa sand 2.65 16.6 ULW-1.75 1.75 11.2

[0147] Large-scale slot flow tests were conducted to characterize thedynamic settling rates of the ultra-lightweight proppant. Proppanttransport characteristics were studied at ambient temperature through aglass slot. The transparent slot is a 22-inch high, 16-ft long and0.5-inch wide parallel plate device. One thousand gallons of test fluidwas prepared and the fluid rheology was measured using a standard Fann35 viscometer. Fluid was then transferred to a 200-gallon capacityribbon blender and pumped through the test loop to fill the transparentslot model. Once the slot was filled with the test fluid, proppant wasadded to the blender to prepare a slurry of the desired concentration.The slickwater fluid used in the test exhibited an average viscosity of5 to 7 cps throughout the series of tests.

[0148] The shear rate in the slot is given by the equation:$\gamma = {\left\lbrack \sec^{- 1} \right\rbrack = \frac{1.925{q\quad\lbrack{gpm}\rbrack}}{\left( {w\quad\left\lbrack {{in}.} \right\rbrack} \right)^{2}\left( {H\quad\lbrack{ft}\rbrack}\quad \right.}}$

[0149] where q is the rate in gallons per minute, w is width in inchesand H is height in feet. Fluid velocity through this slot model is givenby:${v\left\lbrack {m\text{/}\sec} \right\rbrack} = \frac{0.00815{q\quad\lbrack{gpm}\rbrack}}{{\left( {w\quad\left\lbrack {{in}.} \right\rbrack} \right)^{2}\left( {H\quad\lbrack{ft}\rbrack} \right)}\quad}$

[0150] The proppant transport behavior of each test slurry was observedthrough the slot at various flow rates. During these tests, the proppantdistribution was continually recorded with video cameras as well asmanually by observation. All bed height measurements for this work weretaken close to the discharge end of the slot flow cell.

[0151] Ottawa sand slurried in slickwater was observed to begin settlingupon entrance to the slot even at the maximum fluid pump rate. Within 12minutes at 90 gpm (378 sec1 shear rate), the bed height was 15 inches,68% of the total height of the 22 in. slot. Table 4 below shows theresults in tabular form. Only at shear rates in excess of 1000 sec-1 wasthe dynamic Ottawa Sand proppant fall rate mitigated in the slickwatertest fluid. As flow rates were lowered to 30 gpm, the Ottawa proppantbed reached its maximum bed height of 19.5 inches or 91.25% of the slotheight. Above the proppant bed, the shear rate reached 1,414 sec-1, atwhich point additional settling did not occur. As the rate increasedfrom 30 to 40 gpm (1,919 sec-1), the bed height was actually reduced.TABLE 4 Time, Fluid Rate Prop Bed Slot Shear Above bed, minute GpmHeight (ft) Sec-1 sec-1 0 90 0 378 378 1 90 0.25 383 443 12 90 1.25 3811201 14 60 1.27 252 825 18 60 1.38 252 825 19 40 1.39 168 677 28 40 1.54170 1076 30 30 1.58 116 858 42 30 1.67 171 1414 43 40 1.67 171 1919 4540 1.52 169 1070

[0152] The ULW-1.75 test was initiated at 90 gpm. ULW-1.75 was observedto be subject to some settling at 90 gpm, with the bed height growing to4 inches. The fluid rate was lowered to 80 gpm and bed height grew to 6inches. As the rates were reduced incrementally down to 30 gpm, theULW-1.75 bed was observed to grow with reduced rate to 12 inches. Therate was lowered further to 5 gpm and the bed height grew to 19 inchesor 86% of the total slot height. As observed in previous tests, as therate is increased incrementally, bed height decreases due to erosion andfluidization of the bed. The ULW-1.75 results are presented in Table 5.TABLE 5 Time, Fluid Rate Prop Bed Slot Shear Above bed, minute GpmHeight Sec-1 sec-1 0 90 0.0 378 378 7 90 0.33 378 463 8 80 0.38 337 42311 80 0.54 337 478 12 70 0.58 295 432 15 60 0.71 252 412 17 60 0.79 252445 18 50 0.83 210 386 20 50.4 0.92 212 425 22 39 0.96 164 345 23 30 1126 278 28 31 1.29 130 443 29 20 1.33 81 299 33 8 1.44 34 159 34 5.11.46 21 106 35 20 1.54 84 534 37 20.5 1.58 86 640 38 40.4 1.52 170 100640 50.6 1.46 213 1048 45 60.2 1.33 253 933

[0153] Both of the tested materials settle progressively more as thevelocity decreases. Due to the decreased density, the ULW is more easilyplaced back in flow as the rate is increased. The reduced densitymaterials require less shear increase to fluidize the proppant bed.Ottawa sand was observed to require in excess of 1,500 sec-1 totransport the proppant in slickwater and almost 2,000 sec-1 of shear tobegin to fluidize the proppant bed. The ULW-1.75 transporting at shearrates of 500 sec-1 and fluid shear rates of 800 sec-1 were needed tofluidize the proppant bed.

[0154] The data clearly show the advantage of lower density particles inrelation to dynamic sand fall rates. Heavier proppants requiresignificant fluid viscosity, elevated fluid density, and/or high slurryvelocity for effective proppant transport.

[0155] While the invention may be adaptable to various modifications andalternative forms, specific embodiments have been shown by way ofexample and described herein. However, it should be understood that theinvention is not intended to be limited to the particular formsdisclosed. Rather, the invention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of theinvention.

[0156] From the foregoing, it will be observed that numerous variationsand modifications may be effected without departing from the true spiritand scope of the novel concepts of the invention.

1-50. (canceled)
 51. A selectively configured porous particulatecomprising a porous particulate treated with a non-porous penetrating,coating and/or glazing material.
 52. The selectively configured porousparticulate of claim 51, wherein either: (i.) the apparent specificgravity of the selectively configured porous particulate is less thanthe apparent specific gravity of the porous particulate; (ii.) thepermeability of the selectively configured porous particulate is lessthan the permeability of the porous particulate; or (iii.) the porosityof the selectively configured porous particulate is less than theporosity of the porous particulate.
 53. The selectively configuredporous particulate of claim 52, wherein the apparent specific gravity ofthe selectively configured porous particulate is less than the apparentspecific gravity of the porous particulate.
 54. The selectivelyconfigured porous particulate of claim 51, wherein the penetrating,coating and/or glazing material is capable of encapsulating air or alightweight fluid within the porous particulate.
 55. The selectivelyconfigured porous particulate of claim 51, wherein the selectivelyconfigured porous particulate exhibits crush resistance under conditionsas high as 10,000 psi closure stress, API RP 56 or API RP
 60. 56. Theselectively configured porous particulate of claim 55, wherein theselectively configured porous particulate exhibits crush resistanceunder conditions from about 250 to about 8,000 psi closure stress. 57.The selectively configured porous particulate of claim 51, wherein theporous particulate is treated with a liquid and/or curable resin,plastic, cement, sealant, or binder.
 58. The selectively configuredporous particulate of claim 57, wherein the porous particulate istreated with a resin, plastic or binder.
 59. The selectively configuredporous particulate of claim 58, wherein the porous particulate is coatedand/or penetrated with a phenol formaldehyde, melamine formaldehyde,urethane, or epoxy resin.
 60. The selectively configured porousparticulate of claim 57, wherein the porous particulate is penetratedwith nylon, polyethylene or polystyrene or a combination thereof. 61.The selectively configured porous particulate of claim 57, wherein thecoating and/or penetrating material is a liquid having an apparentspecific gravity less than the apparent specific gravity of the porousparticulate.
 62. The selectively configured porous particulate of claim51, wherein the porous particulate comprises a multitude of coatedparticulates bond together.
 63. The selectively configured porousparticulate of claim 51, wherein the strength of the selectivelyconfigured porous particulate is greater than the strength of the porousparticulate.
 64. The selectively configured porous particulate of claim51, wherein the porous particulate has a maximum length-based aspectratio of equal to or less than about
 5. 65. The selectively configuredporous particulate of claim 51, wherein the porous particulate is aceramic or organic polymeric material.
 66. The selectively configuredporous particulate of claim 65, wherein the porous particulate is aceramic.
 67. The selectively configured porous particulate of claim 65,wherein the organic polymeric material is a polyolefin,styrene-divinylbenzene copolymer, polyalkyl acrylate ester, an ethylcarbamate-based resin or a modified starch.
 68. The selectivelyconfigured porous particulate of claim 51, wherein the porousparticulate is a naturally occurring material.
 69. The selectivelyconfigured porous particulate of claim 51, wherein the selectivelyconfigured porous particulate has an apparent density from about 1.1g/cm³ to about 2.6 g/cm³ and a bulk apparent density from about 1.03g/cm³ to about 1.4 g/cm³.
 70. The selectively configured porousparticulate of claim 51, wherein the porous particulate has an internalporosity from about 10 to about 75 volume percent.
 71. The selectivelyconfigured porous particulate of claim 51, wherein the porousparticulate is a relatively lightweight and/or substantially neutrallybuoyant particulate.
 72. The selectively configured porous particulateof claim 71, wherein the apparent specific gravity of the porousparticulate is less than or equal to 2.4.
 73. The selectively configuredporous particulate of claim 72, wherein the apparent specific gravity ofthe porous particulate is less than or equal to 2.25.
 74. Theselectively configured porous particulate of claim 73, wherein theapparent specific gravity of the porous particulate is less than orequal to 2.0.
 75. The selectively configured porous particulate of claim74, wherein the apparent specific gravity of the porous particulate isless than or equal to 1.75.
 76. The selectively configured porousparticulate of claim 75, wherein the apparent specific gravity of theporous particulate is less than or equal to 1.25.
 77. The selectivelyconfigured porous particulate of claim 51, wherein the size of theselectively configured porous particulate is between from about 200 meshto about 8 mesh.
 78. The selectively configured porous particulate ofclaim 51, wherein the coating or penetrating layer is present in theselectively configured porous particulate in an amount of from about 0.5to about 10% by weight of total weight.
 79. The selectively configuredporous particulate of claim 51, wherein the thickness of the coating ofthe selectively configured porous particulate is from about 1 to about 5microns.
 80. The selectively configured porous particulate of claim 51,wherein the extent of penetration of the penetrating material is fromless than about 1% penetration by volume to less than about 25%penetration by volume.
 81. The selectively configured porous particulateof claim 51, wherein the selectively configured porous particulate has aglazed surface.
 82. A sand control particulate comprising at least oneselectively configured porous particulate of claim
 51. 83. A proppantcomprising at least one selectively configured porous particulate ofclaim
 51. 84. A composition for treating a well comprising a suspensionof at least one selectively configured porous particulate of claim 51and a carrier.
 85. The composition of claim 84, wherein the carrier is acompletion or workover brine, salt water, fresh water, or liquidhydrocarbon or a mixture thereof or a gas, a liquefied gas or a foamedgas.
 86. The composition of claim 85, wherein the carrier is a liquidcarbon dioxide based system, carbon dioxide/nitrogen or foamed nitrogenin carbon dioxide.
 87. The composition of claim 84, which furthercomprises a gelling agent, crosslinking agent, gel breaker, surfactant,foaming agent, demulsifier, buffer, clay stabilizer, acid or a mixturethereof.
 88. The composition of claim 84, wherein the carrier fluid is anon-gelled carrier fluid containing a friction reducer.